Receptor-ligand interactions and the education of signal transduction biochemistry are the driving force for all events in cell biology. This is especially true in the immune system, which features numerous receptor- ligand interactions that promote cell-differentiation, proliferation, apoptosis, and activation of effector functions. Accordingly, signal transduction biochemistry is central to understanding the biological events within immune cell homeostasis. The body of knowledge of immune cell signaling has considerably matured over the past ten years, especially with the discovery of the central role for tyrosine protein kinases and the resulting protein-protein interactions. Since it is a nascent field, the techniques used to study signaling events induced by cytokines or other immune cell activators are fairly specialized and perhaps not readily acquired by inexperienced laboratories without direct support. Likewise, given the similarity of assays that apply from one receptor to another, one would hope to benefit from past experience of those studying a like system. Thus, this application proposes a core facility to house expertise and equipment that focuses on immune cell signal transduction biochemistry. It will be used as a knowledge-based and technical resource for new investigators who find a need to explore signaling events in various immune responses and will facilitate development and transfer of expertise and specific assays to a new setting.